Plants herbs or shrubs. Leaves entire. Flowers single or few together in axially cymes; bracts and bracteoles leaflike; calyces 5-lobed, lobes equal; corollas with a short to long tibe widened distally, lobes 5, sybequal; stamens 4. anthers 2-celled, cells parallel. Capsules manyseeds; seeds smooth, flat, orbicular, with mucilaginous hairs, particularly along the margins.
Ruellia includes about 150 species that are primarily tropical in their distribution.